This invention relates generally to performance indicators for rotating shafts, and more particularly to a system and method for monitoring the dynamics of rotating shafts including torque, shaft imbalance and torsional vibration.
In the marine market, existing torquemeters for measuring performance characteristics of rotating shafts, such as a ship""s propulsion shaft, are quite expensive, technically complicated, require significant modification to the shaft, and have poor reliability. Because of these problems, there has been resistance by fleet owners and operators to using or relying on torquemeters. Torque measurements directly off the shaft, however, if done accurately and reliably, can provide much valuable and useful information. Shaft torque variations can provide clues to a variety of equipment conditions such as propeller mismatch or damage, hull fouling, engine cylinder misfiring, bearing problems and overtorque. In twin engine installations torque monitoring on both shafts can allow for more precise engine RPM/torque balancing and for the economics associated with more efficient operation. Over time, comparison of torque/horsepower vs. fuel consumption can allow the fleet owner to save fuel and propulsion equipment by running the vessels at optimum RPM/torque for any given set of conditions or sea states. Sensor data stored by the computer can be analyzed to search for possible patterns of machinery wear and fatigue. Alarm conditions can be programmed into a computer and displayed to the operator when torque limits, RPM limits and sea conditions exceed prescribed limits.
In response to the foregoing, it is an object of the present invention to overcome the drawbacks and disadvantages of prior art rotating shaft monitors.
In a first aspect of the present invention, a performance measuring system for a rotating shaft comprises a first annular support assembly to be coupled adjacent to a first end of a rotating shaft inwardly of associated shaft bearings. A second annular support assembly is to be coupled adjacent to a second end of a rotating shaft inwardly of associated shaft bearings. A third annular support assembly is to be coupled to the rotating shaft and to be interposed between the first and second support assemblies. A laser source is mounted on the first annular support assembly. A laser detector is mounted on the second annular support assembly for generating a first detection signal. A first magnetic sensor for detecting the Earth""s magnetic field is mounted on the first annular support assembly for generating a second detection signal. A second magnetic sensor for detecting the Earth""s magnetic field is mounted on the second annular support assembly for generating a third detection signal. An accelerometer is mounted on the third annular support assembly for generating a fourth detection signal.
In a second aspect of the present invention, a performance measuring system for a rotating shaft comprises a first annular support assembly to be coupled adjacent to a first end of a rotating shaft inwardly of associated shaft bearings. A second annular support assembly is to be coupled adjacent to a second end of a rotating shaft inwardly of associated shaft bearings. A third annular support assembly is to be coupled to the rotating shaft and to be interposed between the first and second support assemblies. A laser diode is mounted on the first annular support assembly. A photodiode or a phototransistor is mounted on the second annular support assembly for generating a first detection signal. A first magnetic spin sensor for detecting the Earth""s magnetic field is mounted on the first annular support assembly for generating a second detection signal. A second magnetic spin sensor for detecting the Earth""s magnetic field is mounted on the second annular support assembly for generating a third detection signal. An accelerometer is mounted on the third annular support assembly for generating a fourth detection signal.
In a third aspect of the present invention, a performance measuring system for a rotating shaft comprises a first split-ring clamp assembly to be coupled adjacent to a first end of a rotating shaft inwardly of associated shaft bearings. A second split-ring clamp assembly is to be coupled adjacent to a second end of a rotating shaft inwardly of associated shaft bearings. A third split-ring clamp assembly is to be coupled to the rotating shaft and to be interposed between the first and second split-ring clamp assemblies. A laser diode is mounted on the first split-ring clamp assembly. A photodiode or a phototransistor is mounted on the second split-ring clamp assembly for generating a first detection signal. A first magnetic spin sensor for detecting the Earth""s magnetic field is mounted on the first split-ring clamp assembly for generating a second detection signal. A second magnetic spin sensor for detecting the Earth""s magnetic field is mounted on the second split-ring clamp assembly for generating a third detection signal. An accelerometer is mounted on the third split-ring clamp assembly for generating a fourth detection signal.
In a fourth aspect of the present invention, a method of performing measurements on a rotating shaft comprising the steps of positioning a laser source on a rotating shaft adjacent to one end of the shaft, positioning a laser detector on the rotating shaft adjacent to the other end of the shaft, positioning a first magnetic spin sensor on the rotating shaft adjacent to one end of the shaft for detecting the Earth""s magnetic field, positioning a second magnetic spin sensor on the rotating shaft adjacent to the other end of the shaft for detecting the Earth""s magnetic field, and positioning an accelerometer on the rotating shaft so as to be interposed between the laser and magnetic spin components. A first detection signal is generated from the laser detector. A second detection signal is generated from the first magnetic spin sensor. A third detection signal is generated from the second magnetic spin sensor, and a fourth detection signal is generated from the accelerometer. The detection signals include information on the level of torque being applied to the rotating shaft. Preferably the information is transmitted to a remote processor for determining whether the torque applied to the rotating shaft is above a predetermined threshold level. If the applied torque is above the predetermined threshold level, preferably an alarm is activated. More preferably, the alarm is audible.
A first advantage of the present invention is that the detectors of the measuring system are mounted directly on the rotating shaft to be monitored, as opposed to the surrounding shaft support system, so as to eliminate the effects of a ship""s structural flexing and vibration on the measurement system.
A second advantage of the present invention is that simplicity of the system, the small size and weight, and the elimination of the necessity to modify the monitored shaft makes the system feasible and practical for smaller workboats.
Other objects and advantages of the present invention will become apparent in view of the following detailed description and accompanying drawings.